An aspect of the invention relates to a data communication device. The data communication device may be, for example, a device that communicates data in accordance with a universal serial bus (USB) standard. Other aspects of the invention relate to a method of manufacturing such a data communication device, a method of data communication, a computer program product, and a data processing system. The data processing system may comprise, for example, a desktop or laptop computer and a security device that exchange data in accordance with the USB standard. The security device may be in the form of, for example, a smartcard in accordance with the ISO7816-12 standard or a token that can be coupled to a USB port of the computer.
United States patent application published under No. 2004/0148539 describes a device that generates a local clock period from a USB downstream-received bit-serial signal. The device does not require the use of a crystal or resonator. Counters are used to determine a first number of periods of a free-running high-frequency clock signal contained within a known number of bit periods of the downstream-received bit-serial signal. The first number of periods is divided by the known number of bit periods of the received bit-serial signal to determine a second number of periods of the free-running high-frequency clock signal comprised in a single bit period of the received bit-serial signal. The local clock period is generated on the basis of the free-running high-frequency clock signal and the second number of periods. The local clock period may be phase-locked with the received bit serial signal. The local period is updated on an ongoing manner by downstream known received traffic.